Inhibition of deposition of water insoluble compounds in aqueous systems

ABSTRACT

DEPOSITION OF WATER INSOLUBLE COMPOUNDS FROM AQUE OUS SYSTEMS CONTAINING THEM IS INHIBITED BY ADDING TO THE AQUEOUS SYSTEM, WHICH MAY BE A SUBSURFACE FORMATION WATER OR BRINE, A SMALL BUT EFFECTIVE AMOUNT OF A PHOSPHATE ESTER OF ETHOXYLATED ESTERIFIED TRIOL OR THE ALKALI METAL OR AMMONIUM SALTS THEREOF.

United States Patent U.S. Cl. 260-403 9 Claims ABSTRACT OF THEDISCLOSURE Deposition of water insoluble compounds from aqueous systemscontaining them is inhibited by adding to the aqueous system, which maybe a subsurface formation water or brine, a small but effective amountof a phosphate ester of ethoxylated esterified triol or the alkali metalor ammonium salts thereof.

BACKGROUND OF THE INVENTION (1) Field of the invention The presentinvention is directed to phosphate esters of ethoxylated esterifiedtriols and the alkali metal and ammonium salts thereof. Moreparticularly, the invention is concerned with inhibition of depositionof water insoluble salts or compounds from aqueous systems containingthem by adding to such systems a phosphate ester of ethoxylatedesterified triol and the alkali metal and ammonium salts thereof. In itsmore specific aspects, the invention is concerned with inhibition ofdeposition of water insoluble compounds in wells, flow lines, and inother equipment containing or through which aqueous media are flowed toprevent fouling by deposition of water insoluble compounds.

(2) Description of the prior art Heretofore, it has been known to usecertain compounds in aqueous systems to alleviate or prevent depositionof water insoluble compounds therefrom such as in wells, well flowlines, conduits, and the like. The same has been true with respect toboiler feed water and other systems. However, such prior art methods andcompounds have not been entirely satisfactory since, especially in oilWells, it is necessary that the inhibitor have the characteristics ofbeing adsorbed on the surface rock formation to a sufficient extent toprovide a sufiicient amount of inhibitor to be effective yet it mustalso be desorbed into the produced W316i or brine such that the producedwater or brine contains a sufiicient amount of the inhibitor to beeffective. Additionally, the inhibitor must also be susceptible toinjection into subsurface rock formation under pressure.

It is also important from an economic standpoint that the inhibitor beeffective in small quantities and be producible from readily availablechemicals without complicated and expensive methods.

The present invention'is quite advantageous and useful in theserespects.

Specific prior art considered with respect to this invention include thefollowing listed U.S. patents: 2,128,161, 3,213,017, 3,258,071,3,258,428, 3,271,306, 3,283,817, 3,288,217, 3,304,349, 3,308,161,3,336,221.

SUMMARY OF THE INVENTION The present invention may be briefly describedand summarized as involving new compounds useful as mhibitors of aqueoussystems from deposition of Water insoluble compounds and involvephosphate esters of ethoxylated esterified triols having the followingformula:

0 5 wnzcnzon-i on OH R O(CH2CH2O)mPOH I h) OH OCR where R is ahydrocarbon radical having 3 to 50 carbon atoms derived from a triolR(OH) R is a long chain organic radical having from 6 to carbon atoms;and

l+m=n and n is the total number of moles of ethylene oxide incorporatedin the molecule in the range from 2 to 30 and the alkali metal andammonium salts thereof.

As an example of a specific compound of the present invention withoutrestricting the invention thereto, the

following structure is given:

In this particular case, the radical R is enclosed in dotted lines andis derived from trimethylol propane. Equally, it may be derived fromother triols.

The invention may also be summarized as involving adding or introducinginto aqueous systems containing water insoluble compounds phosphateesters of the type given above and the alkali metal and ammonium saltsthereof. The aqueous systems may desirably be Water or brine producedfrom a subsurface earth formation or the inhibitor may be injected intothe subsurface formation containing interstitial water or brine to beadsorbed on and desorbed from the rock into the water.

INVENTION VARIABLES In the practice of the present invention, tall oilacid or other fatty or rosin acids are used to esterify triols. Asexamples of organic acids which may be used are those having from 6 to20 carbon atoms in the log chain. Specific acids include by Way ofillustration and not by way of limitation: the rosin acids such asabietic, neoabietic, dehydroabietic, levopimaris, palustric, pimaric,isopimaric, unsaturated fatty acids such as oleic, linoleic, linolenic,saturated fatty acids such as stearic, palmitic, myristic and the like.

The triols useful in the present invention include, trimethylol propane,glycerine, 1,2,4-butane triol, 1,2,6-trihydroxyhexane a ,ot ,octrihydroxyhexamethylbenzene, and the like, and may contain from 3 to 15carbon atoms.

T he inhibitor of the present invention preferably contains from 2 tomoles of ethylene oxide and more preferably 4 to 12 moles for bestresults.

Good results are obtained with the inhibitor present in the aqueoussystem in an amount within the range from about 0.1 to about 50 p.p.m.with best results from about 1 to 20 p.p.m. The amount of the inhibitorused may depend on the particular water insoluble compound in theaqueous system and should be selected to give best results.

The water insoluble compounds and/ or salts commonly encountered inaqueous systems and water and/or brines from oil and/or water wells andthe like include calcium sulfate, commonly referred to as gyp, bariumsulfate, strontium sulfate, calcium carbonate, magnesium carbonate,strontium carbonate, iron carbonate, iron oxide, and the like.

The inhibitors of the present invention may be prepared in accordancewith the following equations:

grams of NaOH used as the cataly The temperature was 240300 F., and thepressure was 60-80 p.s.i.

(3) Phosphorylation: 0.5 mole of the foregoing ethoxylated tall oilester of glycerine was reacted with 2.0 moles of 115% phosphoric acid.The reaction was carried out two hours at.110 C. to give the phosphateester (G) of the present invention.

; .This product G.,was,tested, as an inhibitor for calcium sulfatescale. It was found that l0lp.p.m.-of the inhibitor prepared asindicated above would prevent for 24 hours the precipitation of calciumsulfate from a solution which was supersaturated in CaSO to the extentof 0.06 mole/l. 'lfhe compounds or'inhib'i'tors of the present inventionmay be used as the monoor di-alkali metal or ammonium salts.Particularly, the monoand di-sodium and potassium salts are quiteeffective and useful.

OH (I) CHzOR A B C l ClIzOil-R C D E F The organic acid A is a longchain fatty acid such as a tall oil acid. The amount of ethylene oxidemay range from 2 to moles, but is preferably 4 to 12 moles. In

the several equations, 11 is an integer from 1 to 15 and R is a chainhaving 6 to 20 carbon atoms.

EXAMPLES (1) Esterification: 3.91 moles of tall oil fatty acid (A) wasused to esterify 3.91 moles of trimethylolpropane (B). Toluene sulfonicacid was used as the catalyst and 3.9 moles of water were recovered fromthe reaction mix-' ture during the esterification reaction.

(2) Ethoxylation: 3.87 moles of the ester C' was ethoxylated with 15.4moles of ethylene oxide. Sodium hydroxide was used as the catalyst. Theethoxylation was carried out in a temperature range of 240-300 F. and atation of calcium sulfate from a solution which was 'super-' saturatedto the extent of 0.06 mole/l. for a over 24 hours.

In this example, glycerine was employed instead: of

period of trimethylol propane and an inhibitor inaccordance-with thepresent invention was produced and tested as follows:

(l) Esterification: 3.53 moles tall oil acids was --used to esterify3.86 moles of glycerine. The reactionwas carried out for six hours of200 F. in the presence of 300. g.

of toluene added as a reflux solvent. 3.5 moles of water were collected.After distillation of the toluene, 3.52 rnoles of product wererecovered. p

(2) Ethoxylation: 3.52 of the tall oil ester of glycerine wasethoxylated with 21.2 moles of ethylene oxide with Compound F was usedto inhibit deposition of CaCO from a CaCO solution which depositedscale. In this case, 20p.p.m'. of compound F gave 58% inhibition.

, Coinpou'ndF was further used in inhibiting CaSO deposition from anaqueous system which deposited scale with the following results:

Concentration of inhibitor, p.p.m. Percent inhibition Blank 0 Freshsolution 10 62 Mono K-salt of F, 10 72 Di K salt of F, 10 26 -Di Nasalt'of-F, 10. 86 Blank h 0 f rti inhibito G fl df glycerine as the trimin the present invention is also elfective against calcium sulfatedeposition as shown by the following:

Concentration of inhibitor, p.p.m.

Percent inhibition Inhibitor or G..was.also used as an inhibitor ,ofcalcium carbonate deposition with the following results: p iConcentration of inhibitor, p.p.m. Percent inhibition 20 ;h; 44.0 Blank0 'I'he ,elfectivenesspf. Compound on barium sulfate deposition fromasolution containing 500 p.p.m. BaSO 5% NaCl brine was determined asfollows:

' Concentratio n of inhibitors, p. .m.

30-very slight precipitate after 30 min.

10slight precipitate after 15 min. Blank-heavy precipitate on mixingSolution 1:

200 g. NaCl, AR grade 43.8 g. CaCI -ZH O, USP grade 20.3 g. MgCl -6H O,AR grade Dissolve in distilled water, dilute to 2 liters. Solution 2:

177.5 Na SO AR grade (anhydrous) Dissolve in distilled water, dilute to1 liter.

ml. to titrate sample-blank Percent inhibition= fresh blank blank Theseverity of the test can be increased by placing the bottles in an ovenmaintained at an elevated temperature such as 150 F. for several hours.

Static tests for calcum carbonate inhibition were carried out using asynthetic brine. The tests were done in 6-ounce prescription bottles.The samples on test were heated in an air oven at 160 F. for 20 hours inorder to increase the severity of the test. At the end of the heatingperiod, an aliquot from the test solution was titrated for hardnessusing the standard ethylene diamine tetra acetic acid hardnesstitration. The percent inhibition was calculated by the followingformula:

Sample hardness-blank hardness Fresh blank hardness blank hardnessPercent inhibition= X 100 The test solutions which were used were madeup as follows:

In carrying out a test, 50 ml. of Solution A was placed in a 6-ounceprescription bottle along with the desired amount of inhibitor. Fiftymilliliters of Solution B was then added to the bottle, the bottleshaken well and placed in an oven maintained at 160 F. for 20 hours. Atthe end of this period, the residual hardness was determined using analiquot and the percent inhibition calculated by comparing theperformance of the inhibited sample with the performance of anuninhibited sample.

The hardness was determined by the EDTA hardness titration procedure.

Tests for barium sulfate scale inhibition were carried out using thefollowing procedure.

1 Precipt tlate very [light after 2 hours.

Two test solutions were made up as follows:

Solution 1:

' 50 g. NaCl 0.99 g. BEICIZZHZO to Solution 2:

50 g. NaCl 1.27 g. Na SO -10H O to 1 liter in H O The inhibitor to betested was added to 50 ml. of Solution 1 in a 6-0unce prescriptionbottle. Then 50 ml. of Solution 2 were added to the bottle and thecontents mixed by vigorous shaking.

The degree of inhibition was determined by measuring the length of timerequired for a precipitate of BaSO to become visible in the bottle.

In practicing the presenfinvention to prevent deposition of waterinsoluble salts or compounds in oil well conduits, tubing strings,pumps, and flow lines, the inhibitor as an aqueous solution may beforced or squeezed into a subsurface formation under a pressuresuflicient to inject the inhibitor out into the formation but preferablyinsuflicient to fracture the formation unless the formation has becomeplugged with deposits such as gyp. If the formation has become plugged,it may be desirable to fracture the formation to open up a passage or totreat the formation to open a passage for the inhibitor. After theinhibitor has been adsorbed in and on the rock formation for asuflicient period of time, the well may be placed on production to allowthe inhibitor to be desorbed into the produced water to preventdeposition of gyp.

The inhibitors may also be added to other water handling systems wherescale deposition is a problem.

The nature and objects of the present invention having been completelydescribed and illustrated and the best mode contemplated set forth, whatI wish to claim as new and useful and secure by Letters Patent is:

1. An inhibitor for prevention of deposition of water insolublecompounds from aqueous systems containing them selected from the groupconsisting of phosphate ethoxylated esterified triols having thefollowing formula:

liter in H O I H) OH OC-R Where R is a hydrocarbon radical having 3 to50 carbon atoms derived from a trio R(OH R is a long chain organicradical having 6 to 20 carbon atoms; and l+m=n and n is the total numberof moles of ethylene oxide incorporated in the molecule and is withinthe range from 2 to 30 and the alkali metal and ammonium salts thereof.2. An inhibitor in accordance with claim 1 which is the mono-sodiumsalt.

3. An inhibitor in accordance with claim 1 which is the di-sodium salt.

4. An inhibitor in accordance with claim 1 which is the ammonium salt.

5. An inhibitor in accordance with claim 1 in which the triol has from 3to 15 carbon atoms.

6. An inhibitor in accordance with claim 1 in which the inhibitorcontains from 4 to 12 moles of ethylene oxide.

7. An inhibitor in accordance with claim 1 in which I References Citedthe tIiOl iS trimethylol propane. v 8. An inhibitor in accordance withclaim 1 in which the triol is glycerine 3,215,720 11/1965 Atwood et a1.260461 9. An inhibitor in accordance with claim 1 in which: r ELBERT L,ROBERTS, Primary Examiner (a) the inhibitor is a sodium salt; 0 (b) thetriol has from 3 to 15 carbon atoms; and US. Cl. X.R. (c) the inhibitorcontains from 4 to 12 moles of 2528.55, 180' ethylene oxide.

